Various aspects of the sequence complexity and structure of mRNA's lacking polyA in HeLa and Drosophila cells are being investigated. PolyA minus mRNA's have been found to contain short stretches of oligo A and the location of these sequences within the molecules is being investigated. Hybridization competition experiments between A plus and A minus mRNA to DNA are being conducted to determine if sequences are shared between these two populations. Proteins coded for by A plus and A minus mRNA are being analyzed. The target sizes after ultraviolet light exposure of various RNA populations, including histone mRNA are being analyzed in Drosophila tissue culture cells. Drosophila embryo RNA is being analyzed to determine the state of histone mRNA during embryonic development. Such studies will further our understanding of the fundamental mechanisms of cell growth and development.